In the present study, pharmaceutical waste derived borosilicate glass (BSG) was investigated to fabricate foams without the addition of external foaming agents. Foaming was shown to occur when glass powder compacts were sintered at 950°C and above. It was found that foaming ability depended on the initial powder particle size and it was higher when the glass particle size was <38μm, while samples with a particle size of <100μm and <250μm exhibited bulk nature (no foaming). The exact reasons for the self-foaming behavior of BSG waste were not determined; however a hypothesis was proposed to explain the foaming mechanism. The novel borosilicate glass foams developed here are of interest for acoustic and thermal insulation structures exhibiting high thermal shock resistance.